Photoradiator including light conducting rods with frusto-conical end portions

ABSTRACT

A photoradiator includes a notch at an axial end or in the periphery thereof in order to radiate light which propagates therethrough. Light is radiated in a desired direction and in a desired quantity at the notch. Even the optical property of the light radiated from the photoradiator may be varied for a desired application.

This is a division of application Ser. No. 555,866, filed Nov. 28, 1983.

BACKGROUND OF THE INVENTION

The present invention relates to a photoradiator for effectivelyradiating light propagating therethrough in a desired direction and in adesired quantity to the ambience, while furnishing it with an opticalproperty suitable for a desired application.

Effective use of solar energy is the key to energy saving today and hasbeen studied in various fields actively. For the most effective use ofsolar energy, solar energy has to be availed as it is without beingtransformed into another kind of energy such as thermal energy orelectrical energy. In light of this, I have made various proposals foran illumination system which utilizes solar energy. The illuminationsystem employs a light conducting element such as a fiber optic cablethrough which the sunlight converged by a lens or the like is conductedto a desired location to stream out thereat to illuminate the ambience.

In the illumination system of the type described, the light advancingthrough the light conductor has directivity. Therefore, if the light isoutput at a simple cut end of the light conductor, it becomes radiatedover an angle θ which is usually as small as about 46°. The lightstreaming through the simple cut end of the light conductor would failto evenly illuminate a desired space such as a room. I have proposed invarious forms a photoradiator which is designed to effectively diffuselight conducted by a fiber optic cable to provide even illumination overa wide range.

Another problem encountered with a light conducting element of the kinddescribed is that when it is laid over a length sufficient for practicaluse, fringes develop in the light emanating from the light conductorwhich are undesirable for ordinary lighting applications, although someparticular applications may rather prefer them. Where the lightpropagating through the light guide is a laser or the like, fringesappear therein even if the light conductor is of a very small diametersuch as an optical fiber, rendering the light unfeasible for use with alaser microscope or the like.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide aphotoradiator which is capable of effectively diffusing lighttransmitted therethrough to the outside by means of a simpleconstruction.

It is another object of the present invention to provide a photoradiatorwhich allows light propagating therethrough to be radiated to theoutside in a desired direction and in a desired quantity.

It is another object of the present invention to provide a photoradiatorwhich radiates light having a desired optical property.

It is another object of the present invention to provide a generallyimproved photoradiator.

In one aspect of the present invention, there is provided aphotoradiator comprising a light conducting element which is formed witha notch at one of axially opposite ends thereof, whereby lightpropagating through the light conducting element is radiated from theone end to the outside.

In another aspect of the present invention, there is provided aphotoradiator comprising a light conducting element which is formed witha notch in an outer periphery thereof, whereby light propagating throughthe light conducting element is radiated from the periphery.

In another aspect of the present invention, there is provided aphotoradiator comprising at least two light conducting elements whichare connected serially to each other, at least one of the lightconducting elements being formed with a notch at one end thereof whichconnects to the other light conducting element, whereby lightpropagating through the light conducting elements is radiated at thenotch.

In another aspect of the present invention, there is provided aphotoradiator comprising a light conducting element which is made up ofa cylindrical portion and a frustoconical portion extending tapered fromthe cylindrical portion.

The above and other objects, features and advantages of the presentinvention will become apparent from the following detailed detaileddescription taken with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B to 4A and 4B are views of various embodiments of aphotoradiator in accordance with the present invention, suffix "A"indicating a sectional side elevation and suffix "B", a cross-section;

FIGS. 5-9 are views of other embodiments of the present invention;

FIGS. 10-15 are perspective views of other embodiments of the presentinvention;

FIG. 16 is a perspective view of a modification to a transparent controlmember included in the photoradiator of FIG. 15;

FIG. 17 is a side elevation of the control member of FIG. 16 which ispositioned to reflect incoming light;

FIGS. 18 and 19 are views of a prior art simple cylindrical lightconducting element; and

FIGS. 20A and 20B to 22A and 22B are views of other embodiments of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the photoradiator of the present invention is susceptible ofnumerous physical embodiments, depending upon the environment andrequirements of use, substantial numbers of the herein shown anddescribed embodiments have been made, tested and used, and all haveperformed in an eminently satisfactory manner.

Referring to FIGS. 1A and 1B, a photoradiator embodying the presentinvention is shown and comprises a light conducting element in the formof a rod 10. The light conductor 10 optically connects at one endthereof (not shown) to a source of converged light supply (not shown).The other end of the light conductor 10 is formed with a single conicalnotch 10a in order to effectively diffuse light as will be described.

Light such as sunlight L is converged by a lens or the like into thelight conductor 10 at the source. The light L propagates through thelight conductor 10 while being repeatedly reflected by the rod wall. Atthe notch 10a in the end of the rod 10, the light L is partlytransmitted through the conical surface to the outside and partlyreflected thereby to change its course before being radiated. Statedanother way, the light L propagating through the rod 10 is diffused tothe outside at the conical end 10a over a substantial radiation angle.

A modification to the structure of FIGS. 1A and and 1B is shown in FIGS.2A and 2B. As shown, the light conducting element 10' is formed with anumber of conical notches 10'a at the light outlet end thereof. Theeffect attainable with such a multi-notch structure is essentiallycommon to that achieved with the single notch structure.

In both the structures shown in FIGS. 1A and 1B and 2A and 2B, theconical notch configuration is only illustrative and may be replaced bya polygonal pyramid such as triangular pyramid or quadrangular pyramid.If desired, the notched surface or surfaces may be finished fordiffusion in order to effectively scatter the light to make theillumination tender to the eyes.

The principle described above is similarly applicable to a lightconducting element in the form of a pipe. In FIGS. 3A and 3B, a lightconducting pipe 20 comprises an annular wall 22 the light outlet end ofwhich is cut aslant to define a radially outwardly flared opening 20a.In FIGS. 4A and 4B, a light conducting pipe 20' comprises an annularwall 22' the light outlet end of which is formed with a number ofrecesses or notches 20'a at spaced locations along the circumference ofthe pipe.

In the photoradiator shown in FIGS. 3A and 3B or FIGS. 4A and 4B, theconverged light L such as sunlight propagates through the pipe wall 22or 22' while being repeatedly reflected by the other peripheral surfacethereof. The notch 20a or notches 20'a serve to effectively diffuse thelight L to thereby radiate it to the ambience.

If desired, the embodiment shown in FIGS. 3A and 3B and that shown inFIGS. 4A and 4B may be combined, that is, the light outlet end of alight conducting pipe may be cut to have a flared opening and formedwith a number of recesses along the circumference thereof. Again, thelight outlet end may be finished to serve as a light scattering surfaceand the illustrated notch configuration is only illustrative.

Referring to FIG. 5, another embodiment of the present invention isshown which is applied to a light conducting rod. The light conductor 30in FIG. 5 is formed with a plurality of spaced notches 30a along thecircumference thereof and in a selected position between axiallyopposite ends. Part of light L propagating through the rod 30 is partlydiffused radially outwardly by the walls of the notches 30a. This typeof circumferential notch arrangement is also applicable to a lightconducting pipe, as shown in FIG. 6. The pipe 32 in FIG. 6 is formedwith notches 32a at spaced locations along the circumference thereof andin a selected position between axially opposite ends. The photoradiatorin FIG. 6 functions in the same manner as the photoradiator shown inFIG. 5, except that it reflects the light at both the inner and outerwalls thereof.

In the photoradiator shown in FIGS. 5 or 6, a lower end wall 30a₁ or32a₁ of each notch may be inclined radially outwardly with itsassociated upper end wall 30a₂ or 32a₂ formed perpendicular to thedirection of light propagation as illustrated (to the axis of the lightconductor 30 or 32). Alternatively, the upper end wall 30a₂ or 32a₂ maybe oriented substantially parallel to the inclined lower end wall, asindicated by a phantom line in the drawing. Such a set of notches may belocated at a number of spaced locations along the direction of lightpropagation, or the axis of the light conductor. In this case, theradial depth d of the notches may be sequentially increased in thedirection of light propagation in order to set up substantially uniformradiation of light along the axis of the light conductor.

Referring to FIG. 7, another embodiment of the present invention isshown which has a plurality of light conducting rods (34-38 in thedrawing) interconnected end-to-end in the illustrated order along thedirection of light propagation. As shown, the rod 36 is formed withnotches 36a so that the inclined walls 36a₁ thereof may effectivelydiffuse light coming out from the bottom of the rod 34. Likewise, therod 38 below the rod 36 is formed with notches 38a to diffuse light atthe inclined walls 38a₁ thereof. Such a serial interconnection scheme isapplicable to light conducting pipes as well. As shown in FIG. 8, pipes40-44 are interconnected sequentially along the direction of lightpropagation. The pipe 42 has notches 42a with inclined walls 42a₁ andthe pipe 44, notches 44a with inclined walls 44a₁.

It will be seen that the diffusion of light attainable with thephotoradiator shown in FIG. 7 or 8 is as effective as that attainablewith the photoradiator of FIGS. 5 or 6. Nevertheless, the photoradiatorof FIGS. 7 or 8 is distinguishable over the photoradiator of FIGS. 5 or6 by the easier and more accurate production due to the serialconnection of a plurality of light conducting elements which have beenindividually machined to have the notches.

A modification to the photoradiator of FIG. 8 is illustrated in FIG. 9.As shown, the pipe 40 is connected to the pipe 42 by a light conductingrod 46 whose refractive index is larger than that of the pipe 40.Likewise, the pipe 42 is connected to the pipe 44 by another lightconducting rod 46. The photoradiator having such a construction attainsefficient transmission of light, since the light transmitted through thebore of any pipe is introduced into the annular wall of the adjacentpipe by the rod 46; the pipe walls have a higher light transmissionefficiency than air.

Referring to FIGS. 10-13, other embodiments of the present invention areshown which are commonly designed to diffuse light raidally outwardly tothe ambience. In FIG. 10, the photoradiator comprises light conductingelements 50 and 52 which are connected end-to-end to each other. The endof the element 50 adjacent to the other element 52 comprises a flatsurface 50a, while the end of the element 52 comprises a frustoconicalinclined surface 52a which terminates at a flat top 52b. When the lightconductors 50 and 52 are assembled together, light propagating throughthe light conductor 50 will be partly introduced into the followinglight conductor 52 and the rest is diffused effectively to the outsideby refelection at the inclined surface 52a while being partly routedinto the element 52.

In the photoradiator shown in FIG. 10, the inclination angle 8θ of theinclined surface 52a is variable to steer the light in a desireddirection out of the photoradiator. Where the angle θ is 45 degrees, forexample, the light will be radiated perpendicular to the axis of thephotoradiator if it is parallel light, and over a substantial radiationangle if it is converged light. Also, the ratio in area between theinclined surface 52a and the flat top 52b may be varied to set up anydesired ratio between the quantity of light steered to the outside andthe quantity of light transmitted to the subsequent light conductor.

In FIG. 11, a light conducting element 50' is formed with afrustoconical recess 50'a and a flat surface 50'b which are generallycomplementary to the contiguous frustoconical surface 52a and flatsurface 52b of the light conducting element 52, which is the same as theelement 52 of FIG. 10. In this construction, light propagating throughthe element 50' is partly transmitted to the element 52 via the alignedflat surfaces 50'b and 52b, while the rest is partly refelectedoutwardly by the inclined surfaces 50'a and 52b and partly transmittedinto the element 22. The photoradiator construction shown in FIG. 11 isadvantageous in that it allows the two elements 50' and 52 to be alignedwith ease to each other.

In FIG. 11, should the interconnecting surfaces of the rods 50' and 52be configured fully complementary to each other, no light would berefelected by the inclined surfaces. It is preferable, therefore, todesposit a semitransparent layer on the inclined surface of either oneof the rods 50' and 52. Generally, however, it will suffice to form themapproximately complementary so that an air space may be definedtherebetween to reflect part of the propagating light at the inclinedsurfaces.

In FIG. 13, the photoradiator comprises a cylindrical light conductingelement 54 having a flat end 54a, and a light conducting element 56having two inclined surfaces 56a and 56b which converge to a flat top56c. In this case, light transmitted through the light conductor 54 willbe diffused outwardly in two directions by the inclined surfaces 56a and56b. Again, the light conductor 54 may have its end formed complementaryto that of the light conductor 56 as shown in FIG. 12. In FIG. 12, theelement 54' has a recess defined by opposite inclined surfaces 54'a and54'b and a flat surface 54'c. The construction shown in FIG. 12, likethat shown in FIG. 11, will promote easy alignment between the twocoactive light conductors 54' and 56.

While in the embodiment shown in FIG. 12 or 13 the opposite inclinedsurfaces 56a and 56b are assumed to be equal in area to each other, theymay be provided with different areas such that a larger quantity oflight is reflected by one of them than by the other. In the extremecase, the configuration may be such that the light is reflected by oneinclined surface 60a of a light conducting element 60 as indicated by anarrow A. In this case, light may be supplied from the light conductor 60into an upper light conductor 58 as indicated by an arrow B.

Referring to FIG. 15, another embodiment of the present invention isshown which is furnished with means for controlling a quantity of lightradiation. The photoradiator in FIG. 15 comprises a first lightconducting element 62, a second light conducting element 64 and atransparent control member 68. Either one of the elements 62 and 64 (64in this particular embodiment) is formed with a recess 64a at an endthereof which connects to the other element. The transparent controlmember 68 is removably disposed in the recess 64a. As shown, the controlmember 64 includes a flat surface 68a and an inclined surface 68b. Inthis photoradiator construction, light propagating through the lightconductor 62 is partly transmitted to the light conductor 64 via theflat surface 68a of the control member 68 and the rest is partlyreflected outwardly by the inclined surface 68b while being partlyrouted into the light conductor 64.

A characteristic feature of the photoradiator shown in FIG. 15 is thatthe quantity of light steered by the inclined surface 68b of the controlmember 68 is adjustable by controlling the position of the controlmember 68 in the recess 64a. Light from the light conductor 62 will bepartly reflected by the inclined surface 68b of the control member 68 asindicated by an arrow A, while light from the light conductor 64 will bereflected by the inclined surface 86b as indicated by an arrow B.Therefore, light may be supplied in either one of the oppositedirections as desired.

Another example of the transparent control member is shown in FIG. 16.As shown, the alternative transparent control member 70 comprises twoinclined surfaces 70a₁ and 70a₂ which reflect light from the lightconductor 62 (FIG. 15) in two different directions, as indicated byarrows A. The position of such a control member is adjustable in therecess 64a (FIG. 15) to vary the proportions of the light reflected bythe opposite inclined surfaces 70a₁ and 70a₂ to each other. Again, onlyone inclined surface may be formed on the member 70 in the extreme case.The control member 70, different from the control member 68 of FIG. 15,is incapable of reflecting light coming in from the light conductor 64(FIG. 15), since it would reflect it back thereinto at the inclinedsurfaces 70a₁ and 70a₂ as indicated by arrows B.

It will be apparent that a number of interconnection surfaces eachincluding an inclined surface or surfaces as described may be definedsequentially along the axis of the photoradiator. In such a case, thecontrol member 70 shown in FIG. 16 may be installed in the photoradiatorin the position shown in FIG. 17 to return light reached the last lightconductor n, thereby causing more effective radiation of light. It isnecessary then to treat a flat surface 70b between the inclined surfaces70a₁ and 70a₂ to reflect incident light.

Now, assume a simple cylindrical light conducting element 80 as shown inFIGS. 18 and 19. When parallel light L₁ is introduced into one end A ofthe light conductor 80 as shown in FIG. 18, it will be radiated from theother end B without any divergence. When the incident light is convergedlight as indicated by L₂ in FIG. 19, it will be radiated over adivergence angle θ of about 46 degrees. However, such a simplecylindrical light conductor suffers from the drawbacks previouslydiscussed. Farther embodiments of the present invention will be describewhich are elaborated to radiate light after varying its optical propertyto suit a desired application.

Referring to FIGS. 20A and 20B, the photoradiator comprises a lightconducting element 90 which is made up of a cylindrical portion 90a anda frustoconical portion 90b which extends tapered from the cylindricalportion 90a. When converged light L₂ is incident on an end A of thecylindrical portion 90a, it will propagate through the light conductor90 while being reflected by the wall of the continuous portions 90a and90b. The light output from an end B of the frustoconical portion 90b hasa substantial divergence angle due to the N.A which has increased duringthe travel of the light through the frustoconical portion 90b. Fringeswhich develop in the light output from the photoradiator 90 will befeasible to special decorative applications. For more general lightingapplications, parallel light L₁ may be introduced into the lightconductor 90 as shown in FIG. 20B. The light outgoing the lightconductor shown in FIG. 20B is substantially identical in opticalproperty with the incoming light.

Referring to FIG. 21A, the photoradiator comprises a light conductingelement 92 having a cylindrical portion 92a and a frustoconical portion92b, and a second light conducting element 94 having a cylindricalportion 94a and a frustoconical portion 94b. The light conductors 92 and94 are interconnected at the ends of their frustoconical portions 92band 94b as illustrated. This type of construction eliminates fringes inthe light radiated from the photoradiator, since the fringes developedin the light conductor 92 is cancelled in the second light conductor 94.If desired, use may be made of a single piece light conductor 96 asshown in FIG. 21B, which is identical in configuration with theinterconnected light conductors 92 and 94.

Another embodiment of the present invention is shown in FIG. 22A whichcomprises a light conducting element 98 having a cylindrical portion 98aand a frustoconical portion 98b contiguous with the cylindrical portion98a, and a second light conducting element 100 having a frustoconicalportion 100a, a cylindrical portion 100b and a frustoconical portion100c. This is similar to the construction shown in FIG. 21A except forthe additional conical portion 100c which, as in the construction ofFIG. 20A, serves to increase the radiation angle of output light byreflection. Again, the two light conductors 98 and 100 may be replacedwith a single light conductor 102 configured generally identicalthereto.

Various modifications will become possible for those skilled in the artafter receiving the teachings of the present disclosure withoutdeparting from the scope thereof.

What is claimed is:
 1. A photoradiator for diffusing light transmittedtherethrough comprising a first and second cylindrical light conductingrods each having a longitudinal axis and each having an outercylindrical wall, said first cylindrical light conducting rod having afirst lognitudinal end section, said first longitudinal end sectionhaving an inner frusto-conical wall and an inner flat end wall, saidinner frusto-conical wall having a large diameter end and a smalldiameter end, said large diameter end being coincident with acircumferential line on said outer cylindrical wall of said firstcylidrical light conduting rod, said inner flat end wall having acircular configuration, said smaller diameter end of said innerfrusto-conical wall beng coincident with said inner flat circular endwall, said second cylindrical light conducting rod having a secondlongitudinal end sections said second longitudinal end section having anouter frusto-conical wall and an outer flat end wall, said outerrusto-conical wall having a large diameter end and a small diameter end,the last said large diameter end being coincident with a circumferentialline on said outer cylindrical wall of said second cylindrical lightconducting rod, said outer flat end wall having a circularconfiguration, said small diameter end of said outer frusto-conical wallbeing coincident with said outer flat circular end wall, said innerfrusto-conical wall, along with said inner flat circular end wall, beingcomplementarily arranged and axially aligned respectively with saidouter frusto-conical wall along with said outer flat circular end wall;and a semitransparent layer deposited on either one of said innerfrusto-conical wall of said first cylindrical light conducting rod andsaid outer frusto-conical wall of said second cylindrical lightconducting rod, whereby light propagating through said first cylindricallight conducting rod is transmitted to said second cylindrical lightconducting rod via said inner and outer flat circular end walls whilethe rest of the light being propagated is partly reflected laterallyoutwardly by said inner and outer frusto-conical wall via saidsemitransparent layer and partly transmitted through said inner andouter frusto-conical walls and said semitransparent layer into saidsecond cylindrical light conducting rod.
 2. A photoradiator fordiffusing light transmitted therethrough comprising first and secondcylindrial light conducting rods each having a longitudinal axis andeach having an outer cylindrical wall, said first cylindrical lightconducting rod having a first longitudinal end section, said firstlongitudinal end section having an inner frusto-conical wall and aninner flat end wall, said inner frusto-conical wall having a largediameter end and a small diameter end, said large diameter end beingcoincident with a circumferential line on said outer cylindrical wall ofsaid first cylindrical light conducting rod, said inner flat end wallhaving a circular configuration, said small diameter end of said innerfrusto-conical wall being coincident with said inner flat circular endwall, said second cylindrical light conducting rod having a secondlongitudinal end section, said second longitudinal end section having anouter frusto-conical wall and an outer flat end wall, said outerfrusto-conical wall having a large diameter end and a small diameterend, the last said large diameter end being coincident with acircumferential line on said outer cylindrical wall of said secondcylindrical light conducting rod, said outer flat end wall having acircular configuration, said small diameter end of said outerfrusto-conical wall being coincident with said outer flat circular endwall, said inner frusto-conical wall being fully complementary with saidouter frusto-conical wall, and a semitransparent layer deposited oneither one of said inner frusto-conical walls of said first cylindricallight conducting rod and said outer frusto-conical wall of said secondcylindrical light conducting rod, said first and second cylindricallight conducting rods being disposed in an axially aligned position withsaid inner frusto-conical wall being separated from said outerfrusto-conical wall by said semitransparent layer and with both saidinner and outer frusto-conical walls in contact with saidsemitransparent layer, whereby light propagating through said firstcylndrical light conducting rod is transmitted to said secondcylindrical light conducting rod via said inner and outer flat circularend walls while the rest of the light being propagated is partlyreflected laterally outwardly by said inner and outer frusto-conicalwall via said semitransparent layer and partly transmitted through saidinner and outer frusto-conical walls and said semitransparent layer intosaid second cylindrical light conducting rod.
 3. A photradiator fordiffusing light transmitted therethrough comprising first and secondcylindrical light conducting rods each having a longitudinal axis andeach having an outer cylindrical wall, said first cylindrical lightconducting rod having a first longitudinal end section, said firstlongitudinal end section having an inner frusto-conical wall and aninner flat end wall, said inner frusto-conical wall having a largediameter end and a small diameter end, said large diameter end beingcoincident with a circumferential line on said outer cylindrical wall ofsaid first cylindrical light conducting rod, said inner flat end wallhaving a circular configuration, said small diameter end of said innerfrusto-conical wall being coincident with said inner flat circular endwall, said second cylindrical light conducting rod having a secondlongitudinal end section, said second longitudinal end section having anouter frusto-conical wall and an outer flat end wall, said outerfrusto-conical wall having a large diameter end and a small diameterend, the last said large diameter end being coincident with acircumferential line on said outer cylindrical wall of said secondcylindrical light conducting rod, said outer flat end wall having acircular configuration, said small diameter end of said outerfrusto-conical wall being coincident with said outer flat circular endwall, said first and second cylindrical light conducting rods beingdisposed in an axially aligned position with an air space between saidinner frusto-conical wall and said outer frusto-conical wall, wherebylight propagating through said first cylindrical light conducting rod istransmitted to said second cylindrical light conducting rod via saidinner and outer flat circular end walls while the rest of the lightbeing propagated is partly reflected laterally outwardly by said innerand outer frusto-conical wall via said air space and partly transmittedthrough said inner and outer frusto-conical walls and said air spaceinto said second cylindrical light conducting rod.